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CHICAGO — U.S. scientists say a dramatic result last year suggesting that a cancer drug already
approved by U.S. regulators could quickly clear out Alzheimer’s plaques in mice was too good to be
true.

The study, published last year in the journal
Science, showed that the skin-cancer drug bexarotene cut the amount of an Alzheimer’s
-linked protein called beta amyloid by half in three days. It also reversed Alzheimer’s symptoms,
restoring a sense of smell in treated mice.

The news sent patients clamoring for the drug, and some doctors began prescribing it, even
though it had not been tested in people with Alzheimer’s.However, researchers at several U.S.
centers reported in the same journal yesterday that they were unable to reproduce the most-dramatic
aspects of the findings.

Gary Landreth and colleagues at Case Western Reserve University in Cleveland, the scientists
behind the original research, say the drug still has merit, noting that the latest studies
confirmed other aspects of the research showing that the drug cleared out soluble forms of beta
amyloid from the brain.

Scientists say the controversy underscores the desperation of Alzheimer’s sufferers to find
effective treatments for the fatal, brain-wasting disease.

The new research failed to find any effects on Alzheimer’s plaques in mice that were treated
with bexarotene.

“There is absolutely no reduction in amyloid levels in the brains of mice treated with this
compound,” said Sangram Sisodia, a professor of neuroscience at the University of Chicago.